This invention relates to an improved method of fabrication of cylindrical grooved sections provided with longitudinal recesses or with helical recesses with either a direct or alternate pitch, said recesses being almost closed with peripheral opposing lips which come into contact with each other. A structure of this type is primarily intended to be employed as a support for optical fiber communication cables such as, for instance described in U.S. patent Application Ser. No. 877,872 filed on Feb. 15, 1978 entitled: "Cable incorporating optical fibers".
The U.S. patent Application Ser. No. 797 filed on Jan. 3, 1979 entitled: "Method of continuously machining supports for electromagnetic waves guides" discloses a method for the continuous machining of grooves in a solid cylindrical section by removal of material. This operation is carried out by means of a machining head which is designed for rotating about the axis of the cylinder and comprises tools for cutting said grooves. The method thus described is limited to the fabrication of grooved sections having outwardly open grooves.
The object of the present invention is to form lipped recesses in a grooved section during the extrusion operation without any reduction in the linear extrusion speed and without further machining step.